Raman Computational and Experimental Studies on Label-Free Biological Investigations

John Ciubuc, University of Texas at El Paso

Abstract

Raman spectroscopy is an optical technique that allows for label-free biological investigations to take place. This approach presents both new perspectives and a means for visualizing investigations. This thesis confronts two biological cases: dopamine (DA) detection at physiological levels and assessment of renal osteodystrophy (ROD). We employed surface-enhanced Raman spectroscopy on silver nanoparticles recording DA concentrations as low as 10−11 molar. Quantum chemical density functional calculations were carried out using Gaussian-09 analytical suite software. Good agreement between the simulated and experimentally determined results indicates the existence of distinct DA molecular forms, such as uncharged DA±, anionic DA−, and dopaminequinone. Disappearance of the strongest bands of dopamine around 750 cm−1 and 790 cm−1 suggests its adsorption onto the metallic surface. Not only is this consistent with the DA configurations mentioned but also presents additional information about the analyte’s redox process and voltammetric detection. On the other hand, occurrence of the above-mentioned Raman lines could indicate DA multi-layer formation or its presence in a cationic DA+ form. ROD requires a different approach, due to difficulties in defining the pathogenesis and treatment efficacy, since there are many factors that affect bone quality. We used confocal Raman microscopy and parallel statistical analysis to identify differences in bone composition between healthy and ROD bone tissues. Three main compositional parametric ratios are directly visualized: calcium content, mineral-to-matrix, and carbonate-to-matrix. Besides the substantially lower values found in ROD specimens for these representative ratios, an obvious accumulation of phenylalanine is Raman spectroscopically observed for the first time in ROD samples and reported here. Since the image results are based on tens of thousands of spectra per sample, not only are the average ratios statistically significant between the normal and ROD bone, but the method is powerful in distinguishing between the two types of samples. The statistical outcomes demonstrate that only a relatively small number of spectra need to be recorded to classify the samples. The biological investigations completed pave way towards valuable future developments. Through coordinated experiment and theory, remarkable insights are obtained through observing DA vibrational signatures changes. These insights allow for a better understanding of its detection at physiological levels, which is crucial if a further optovoltammetric medical device development is envisioned. Furthermore, this work opens the possibility of future development of in vivo Raman sensors for assessment of bone structure, remodeling, and mineralization, where various biomarkers are simultaneously detected with unprecedented accuracy.

Subject Area

Biomedical engineering|Public health|Pathology|Health sciences|Neurosciences|Epidemiology|Physiology|Medicine

Recommended Citation

Ciubuc, John, "Raman Computational and Experimental Studies on Label-Free Biological Investigations" (2019). ETD Collection for University of Texas, El Paso. AAI13878321.
https://digitalcommons.utep.edu/dissertations/AAI13878321

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